This protocol is designed to compare different methods for managing a patient in whom a central venous catheter has been inserted and to determine the optimal clinical life span of such catheters. The primary goal is to assess whether the incidence of infection differs when catheters are replaced only when clinically necessary compared to replacement on a regular (i.e., weekly) schedule. A second goal is to examine whether sequential replacement of catheters over guide wires results in a different incidence of infection than sequential replacement at new sites. The study population consists of Clinical Center patients who require central venous catheters for clinical indications; the study randomizes the frequency and manner of catheter replacement. The outcome variables are catheter insertion site infections and catheter related bacteremia or fungemia. The design of the study also will allow re-evaluation of the use of semiquantitative catheter cultures as a means of identifying catheters sufficiently colonized to be a source of septicemia. More than 100 patients have been randomized into this study within the first year of its implementation. It is anticipated that another Washington-area hospital will implement the same study protocol during 1994.